African Deception!

I received a phone call from African bank Ch last year 2019 offering me a discount on the settlement of my credit card, which I excepted a higher than usual debit order to settle this account. They debited this amount however I saw that my balance remains the same. Never settled! When I queried this, I was told that I should paid. How can I should pay if they debited my account? The supervisor called me and acknowledged her error mistake promising that she would refund me the extra amount taken and close the account. This has still not been done. I Phoned the call centre who is agents are are as gatekeepers for the supervisor and refuse to transfer me to the supervisor. All I want is my money back and for this matter to be resolved. TG MPITU